Generalised Payne shift inequality for buckling eigenvalues

Let $\Omega\subset\mathbb R^d$ be a domain of finite measure, and let $\lambda_k^{(m,t)}(\Omega)$ denote its $k$th buckling eigenvalue. Generalised Payne buckling inequality. For every $k,m,t\in\mathbb N$,

$$\lambda_{k+1}^{(m,t)}(\Omega)\leq\lambda_k^{(m+1,t)}(\Omega).$$

This is a proposed all-eigenvalue extension of the shift-type inequality comparing successive operator orders. The source attributes the conjecture to considerations involving the Dirichlet Laplacian and cites Friedlander and Liu; its resolution is not established in the supplied material.